Protective apparatus



3 Sheets-Sheet4 l Filed .Dec 13 1932 e, u m www. m n .t mw A 1w .m R H July 24, 1934. R, WlDERE 1,967,849

PROTECTIVE APPARATUS Filed Dec. 13, 1932 3 Sheets-Shea?l 2 July 24, 1934. R, W|DERE 1,967,849

IROTECTIVE APPARATUS Filed Dec. 13, 1932 5 Sheets-Sheet 3 Fig; 6.

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Patented July 24, 1934 time PROTECTVIE APPARATUS Rol! Widere, Berlin-Karishorst, Germany, assignor to General Electric Company, a corporation of New Yori:

Application December l 3, 1932, Serial No. 647,04

Germany December 21, 1931 My invention relates to improvements in protective apparatus and more particularly to improvements in fault responsive apparatus whose operation is so dependent on the function of the currentl and the voltage of a circuit as to provide an action based on an impedance characteristic of the circuit.

The known reactance-dependent relays are similar to ohmmeters in design. Current and voltage are applied to separate coils which exert .a torque acting upon a movable system and causing it to operate when an impedance characteristic of a circuit differs from a predetermined value. Relays of this kind are comparatively complicated especially when a high degree of sensitivity is required. One object o! my invention is to cause reactance to act directly upon a relay which is of more simple construction My invention is based on the tact that the voltage of a circuit satisfies the equation cli B-R-l-La-" Thus di Lai i di y and the other proportional to the power system Voltage, both of the voltages being active only approximately at the moment the current 'passes r through zero.

My invention will be better understood from the following description when considered in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.

In the accompanying drawings, Figs. l. and 2 are curve diagrams explanatory of my invention, Fig. 3 illustrates diagrammatically a protective arrangement embodying my invention; Figs. 4 and 5 illustrate modiiications in parts of my invention, and Fig. 6 illustrates another, modification of my invention.

'Ihe diagram of Fig. 1 shows curves of the voltages which I employ in protective arrangements embodying my invention. The curve 10 represents that is the rate of change of current. The curve 11 represents the circuit voltage e. A third voltage represented by the curve 12 is dependent on the rectified circuit current. This third voltage which acts as an operation-preventing or devicelocking voltage is added to the rst two mentioned voltages. The purpose of this third voltage is to hold the device and to release it only when the thirdV voltage is approximately zero. Thus, in the vicinity of zero, that is, substantially in the zone a, the release depends merely upon the relation between the voltages 10 and 11, that is upon Q y dt or the reactance. of' the circuit under control. With the voltages as illustrated in Fig. 1, a response would occur at each zero point of the curve 12, since the bias of the voltage 12 then disappears, rst in one sense and then in the other with respect to the dierence between the voltages '10 and 11. To avoid this, the curve 11 within the zone operating in the sense of release is either eliminated or reversed, as shown by the dashed line 13I in Fig. 1. l

The algebraic sum of the instantaneous values of all the voltages may be applied to a polarized relay or 'to an electric-discharge valve having a control electrode. An illustrative example embodying a discharge valve is shown in Fig. 3. An alternating current circuit which includes conductors 14 and 15, and which is shown singlephase for the sake of simplicity, has connected thereto a current transformer 16 and a potential transformer 17. A resistance 18 and an inductance coil 19 are connected ln the secondary circuit of the current transformer 16. Four suitable rectiers- 20, examples of which are wellknown to the art, are connected across the resistance" 18 for full-wave rectication. An impedance 21 is connected to these rectiers. Consequently the voltage across the impedance is proportional to the rectted current in each half-wave as shown in curve 12 of Fig. 1. The voltage across the inductance coil 19 is proportional to the circuit current and is phase displaced substantially 90 therefrom. In other words, it is proportional to the rate of change of the circuit current or i* de and is as shown by the curve 19 of 1. The

l voltage transformer 17 has two secondary windf pedance so that the voltage across this impedance corresponds to the circuit voltage. This voltage may be indicated for a half cycle by the dashed line 13 in Fig. 1. lf the algebraic sum of the instantaneous values of the voltages across the impedance devices 19, 21 and 25 is applied between the control electrode 26 and the cathode 27 of an electric discharge valve 28, and a bias battery 29 gives the valve a voltage which causes it to come into operation only `when a voltage is produced in a given direction, that is when the circuit current is predominant, then the valve 28 comes into operation, that is it becomes conductive only when the reactance of the circuit lll, 15 is below a predetered value.

In the embodiment of my invention shown in Fig. 3, the control electrode circuit has applied thereto a further voltage which is taken from the secon winding 23 of the potential transformer 17. A resistance 30 in the circuit of the unnding 23, an inductance coil 3l, a rectifier 32 andan impedance 33 cooperateA to render this voltage proportional to a rectified half wave of the circuit voltage. The arrangement is such that according to the direction of the flow of current which vblocks the valve, the'mum value on this voltage coincides with the positive or neger tive maximum of the voltage acting to start the valve or render it conductive.

The induence of this voltage is shown by curve 9 of Fig. 2. In a certain position, the voltage 9 prevents the valve from being started, depending upon whether this voltage is produced at the moment the curve l2 passes through zero. Under the conditions illustrated in Fig. 2 the curve 9 is so positioned that it does not prevent the operation of the valve from being eiected at the point a by the voltage lo. This operation is opposed merely by the value of the voltage ll. When, however, a change in the direction of the current relatively to the voltage causes the curve `9 to shift to such an extent that its voltage is active at the moment the curve 12 passes through zero, then it opposes the starting of the valve. Thus the reactance-operated arrangement is also caused to operate in dependence upon the direction of energy flow by the addition ofthe voltage 9, that is, the voltage across the impedance 33, as shown in Fig. 3. This directional feature is disclosed and claimed in my copending applicaltion, Serial No. 647,041, led December 13, 1932,

and assigned to the assignee of this invention.

To make zonen as small as possible, the slope of thecurves 12 and 9 may be made as steep as possible. This can be obtained hy selecting large amplitudes, that is the resistance 18 and the impedance 33 are chosen to provide high voltage drops. In order that the `rrectiers 20 and the valve 28 may not be subjected to excessive voltages on'the occurrence of faults within the protective zone, it is preferable that the crests of the curves 12 and 9 be attened. 'Ihis can be done by having the resistances 18 and 30 so voltagedependent that their ohmic values decrease with neonato increasing voltage. Examplesof such resistances are `vvell known to the art, one suitable for the purpose being disclosed in United States Letters Patent 1,822,742, issued September 8, 1931.

As shown in Fig. 3, the releasing -device to be operated by the anode current of the valve 23 is the trip coil 34 of a circuit breaker 35 arranged to control the circuit 141, 15. The characteristics of the trip coil may be such that the anode current of the valve is not sumcient to effect the operation of the trip coil directly as very sensitive discharge valves generally provide a small anode current. lt is, therefore, suitable, as shown in Fig. 4l, to have the valve 28 control another valve 36. For this purpose a resistance 37 is connected in series in the anode-cathode circuit of the valve 28 and one terminal of the resistance is connected tothe control electrode of the valve 36. The

anodes of both of the valves 28 and 36 are con-' nected together and the cathode of the valve 36 is connected to the negative pole of the anode source. As soon as the valve 28 becomes conductive, the voltage drop across the resistance 37 reaches a value sumcient to cause the valve 36 `to become conductive and the anode current supplied thereby is great enough to operate the trip coil 34.

ln place of the valve 23 there may be connected to the auxiliary circuit conductors 38 and 39, as shown in Fig. 5, the operating winding 40 of a sensitive polarized relay 41, examples of which are well known to the art. The contacts 42 of this relay, as will be obvious to those skilled in the art, may be connected to control the circuit of the trip coil 34.

1t is obvious from Figs. 1 and 2 that when only one half wave or the voltage 1l is rectined, there is always a discharge of the valve after one full cycle. When the discharge valve is of the ordinary type (for example a pure electron discharge valve), the current impulse produced at the end of each cycle furnishes for a short time an `anode current through the releasing or tripping circuit. en the discharge valve is of the gas or vapor-hlled type, a continuous anode current flows after one discharge but the discharge y often take place only after more than onehalf wave following the occurence of the fault. As'shown in Fig. 6, shorter response times can be obtained by providing a second valve 43 upon the control electrode of which all the voltages act oppositely so that the response times of the two tubes have a relative time displacement of onehalf wave. The voltages applied to the control electrode of the valve 28 as will be obvious from the gure are the same as those of Fig. 3 but the inductance coil 19 now takes the form of an insulating transformer 19' which is so connected to the impedance 21 as to obtain the necessary displacement at the control electrode of the valve 43. Similarly the rectiiiers 24' and 32 are reversely connected to impedances 25' and 33 corresponding to the impedances 25 and 33. Obviously, in this arrangement the anode circuit may also be arranged as shown in Fig. 4, that is with an additional valve 36 capable of carrying high anode currents and allowing the use sensitive valves 28 and 43.

While I have shown and described my invention in considerable detail, I do not desire to be limited to the exact arrangements shown but seekto cover by the appended claims all those modiof highly cations that fall within the true spirit and scope of my invention.

WhatIclaimasnewanddesiretosecureby Letters Patent of the United States is:

1. In combination with an alternating current electric circuit, means for deriving from said circuit a voltage dependent on the rate of change of the circuit current, a voltage dependent on the circuit voltage, a'voltage dependent on the rectication of both half waves of the circuit current and a voltage dependent on a rectified half wave of the circuit voltage whose maximum value occurs substantially simultaneously with one of the maximum values of the voltage derived from the rate of change of circuit current and electroresponsive means connected to be energized in accordance with the algebraic sum of the instantaneous values of said derived voltages.

2. In combination with an alternating current electric circuit, means for deriving from said circuit a voltage dependent on the rate of change of the circuit current, a voltage dependent on a rectiiied half wave of the circuit voltage, a voltage dependent on the rectication of both half waves of the circuit current and a voltage dependent on a rectified half wave of the circuit voltage whose maximum value occurs substantially simultaneously with one of the maximum values of the voltage derived from the rate of change of circuit current and an electric discharge valve hav-l ing a control electrode connected to be energized in accordance with the algebraic sum of the instantaneous values of said derived voltages.

3. In combination with an alternating current electric circuit, means for deriving from said circuit a voltage dependent on the rate of change of the circuit current, a voltage dependent on the circuit voltage, a voltage dependent on the rectication of both half waves of the circuit current and a voltage dependent on'a 'rectified half wave of the circuit voltage whose maximum value occurs substantially simultaneously with one of the maximum values of the voltage derived from the rate oi change of circuit current, electrore.- sponsive means connected to be energized in accordance with the algebraic sum of the instantaneous values of said derived voltages and cooperating electroresponsive means connected to be energized in accordance with the algebraic sum of the instantaneous values of voltages angularly displaced substantially 180 from said derived voltages.

4. In combination with an alternating current electric circuit, means for deriving from said circuit two voltages respectively dependent on the rate of change of the circuit current and on the circuit voltage, electroresponsive means connected to be energized for operation in accordance with the relation between said two voltages andy Vsponsive means only approximately at the moment the circuit current is passing through its zero value.

5. In combination with an alternating current electric circuitmeans for deriving from said circuit two voltages respectively dependent on the rate of change of the circuit current and on the circuit voltage, electroresponsive means connected to be energized for operation in accordance with the balance between said two voltages, means for selecting a predetermined portion of the wave ci one of said voltages to control the energization of said electroresponsive means and means for permitting said voltages to become eiectiveli7 operative to'control said electroresponsive means only approximately at the moment the circuit current isipassing through its zero value.

6. In combination with an alternating current electric circuit, means for deriving from said circuit two voltages respectively dependent on the rate of change of the circuit current `and on thecircuit voltage, electroresponsive means connected to be energized for operation. in accordance with the relation between said two voltages, means for rectifying a predetermined half wave of a voltage dependent on the circuit voltage to control the energization of said electroresponsive means and means for rectifying both half waves of a voltage dependent on the circuit current further to control the energization of said electroresponsive means.

7. In combination with an alternating current electric circuit, means for deriving from said circuit two voltages respectively dependent on the rate of change of the circuit current and on the circuit voltage, electroresponsive means connected to be energized for operation in accordance with a predetermined function of said voltages, means for rectifying a predetermined half wave of the voltage dependent on the circuit voltage to control the energization of said electroresponsive means, means for deriving a voltage dependent on the rectification of both half waves of a voltage dependent on the circuit current further to control the energization of said electroresponsive means and means for deriving a fourth voltage dependent on the rectified half wave of a voltage dependent on the circuit voltage whose maximum value occurs substantially simultaneously with one of the maximum values of the voltage derived from the rate of change of the circuit current still further to control the energization of said electroresponsive means.

8. In combination with an alternating current electric circuit, means for deriving from said circuit two voltages respectively dependent on the rate of change of the circuit current and on the circuit voltage, electroresponsive means connected to be energized for operation in accordance with a predetermined function of said voltages, means for rectifying a predermined half wave of the voltage dependent on the circuit voltage to control the energization of said electroresponsive means, means for deriving voltage dependent on the rectification of both half waves of a voltage .v1-i dependent on the circuit current further to control the energization of said electroresponsive means, means for deriving a fourth voltage dependent on the rectified half wave of a voltage dependent on the circuit voltage wlio maximum value occurs substantially simultaneously with one of the maximum values of the voltage derived from the rate of change of the circuit current still further to control the energization ci said electroresponsive means and means for flattening the crest of the wave of one of the last two mentioned derived voltages.

9. In combination with an alternating current .electric circuit, means for deriving from said circuit two voltages respectively dependent on the rate of change of the circuit current and on the circuit voltage, electroresponsive means connected to be energized for operation in accordance witli a predetermined function oi said. vole, means for rectifying a predeteed haii wave of voltage dependent on. the circuit voltage to control the energization of said electroresponslve means, means for deriving a voltage dependent on rectification of both half waves of a voltage dependent on the circuit current further to con- Mii for contro said circuit, means for deriving from said circuit two voltages respectively dependent on the rate of change oi the circuit current and on the circuit voltage, electroresponsive means for controlling said circuit interrupting means in accordance with the balance between said two voltages and means for permitting said voltages to become eectively operative to control said elecuoresponsive me only approximatelv at the moment the circuit current is passing through its zero value.

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